An escalator or an autowalk is widely used in people's daily life, and it is used to carry passengers from one height to another, or to carry passengers from one end to the other. The driving device of the escalator or autowalk usually includes a motor, gears, stairsteps or plate driver module, and an armrest driver module, etc. At present, monitoring the driving device of the escalator or autowalk is mainly to obtain for example rotation speeds or rotation directions of the motor, so as to monitor and get rid of the faults of overspeed or inversion, etc.
However, an abnormal movement or displacement may also occur in the driving device per se of the escalator or autowalk. For example, in a horizontal direction, the driving device may have an overtravel movement, that is to say, the movement of the driving device in a horizontal direction exceeds the scope of its normally allowed movement. For another example, the driving device may also have an upthrust under the action of external force. These abnormal movements mean that failure or damage may have occurred in the driving device and/or a device associated with it, while this kind of failure or damage will bring a large security risk, and thus it is necessary to monitor the abnormal movements of the driving device to timely find and get rid of the failure, thereby ensuring the safety of the passengers.